Intramedullary nails including fixation screws inserted through the intramedullary nail in a transverse direction to lock the intramedullary nail relative to the bone are commonly known. In particular, proximal humerus nails comprise multiple fixation screws arranged at different angles relative to each other in the proximal part of the intramedullary nail to securely fixate bone fragments.
These screws are positioned in the intramedullary nail in corresponding through holes using an aiming arm or aiming block rigidly connected to the proximal end of the intramedullary nail by an intermediate member. These aiming blocks feature guiding holes aligned with the through holes in the intramedullary nail but arranged at a distance from the bone to leave space for the arm and shoulder of the patient. Generally, drilling or guiding sleeves are inserted into the holes in the aiming block drilling tools and screwdrivers guided through the sleeves are exactly aligned with the holes in the intramedullary nail. For anatomical reasons, intramedullary nails are commonly provided in “left” and “right” embodiments, i.e. in a mirrored configuration. Therefore, the aiming blocks generally feature through holes matching the left side and the right side configurations of the intramedullary nail. Because aiming blocks which preferably include radiolucent carbon fibre reinforced PEEK material are very costly, it is preferred to have only one aiming block for both configurations of the intramedullary nail. Known aiming instruments comprise aiming blocks with all the through holes for the left side and the right side configurations of the intramedullary nail in a single aiming block. These known aiming blocks can pose the risk that the wrong through holes may be used when preparing the bone, i.e. drilling the holes in the bone through which the fixation screws will be positioned. For example, a user may inadvertently drill through a hole corresponding to the “right side” configuration of the aiming device while working with a “left side” intramedullary nail. If a wrong hole is selected the drill bit will collide with the intramedullary nail and cause unacceptable debris possibly resulting in a loss of stability of the intramedullary nail and furthermore, an unnecessary hole drilled into the bone. In order to prevent this, the through holes in the aiming block are clearly marked “left” and “right” or are colour coded. In stressful situations, however, mistakes may still be made.
German Patent No. DE 101 10 246 C2 ERHARDT discloses an aiming device for a tibial locking nail which can be used for placing locking screws for the left as well as for the right tibia using the same device. However, the tibial nail used with the system of ERHARDT is of the single type and does not have different left and right side shapes.